Congress hasn't budged in the five weeks since President Barack Obama asked Congress for more than $1.8 billion in emergency funding to deal with the Zika virus. But Zika isn't waiting.

In the weeks since the president's request, the number of cases of the mosquito-borne virus among people who traveled to countries where transmission has been confirmed has almost quadrupled to 193, as of March 9. It is in nearly twice as many states -- 32 and the District of Columbia -- with Florida, New York and Texas topping the list. In Puerto Rico, the U. S. Virgin Islands, and American Samoa, the number of cases is 174, or 19 times higher, reports the US Centers for Disease Control and Prevention.

"We are scraping together every dime we can to respond to this," CDC director Dr. Tom Frieden said last week in a conference call with reporters. "But it makes it very difficult to do things like plan for large-scale mosquito-control activities in Puerto Rico [and] establish and support rapid response teams to respond to clusters in the United States."

Zika virus has been linked with microcephaly, a rare birth defect among newborns that causes brain deformities. But Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, who joined Frieden on the call, cited recent studies linking Zika to other fetal abnormalities and Guillain-Barre syndrome, which causes paralysis.

"As the weeks and months go by, we learn more and more and realize how much we don't know," Fauci said. "And unfortunately, the more we learn, the worse things seem to get."

He is "cautiously optimistic" about developing a vaccine for Zika and expects to begin a phase one trial to determine the drug's safety and immunogenicity by early fall, with results possibly by the end of 2017. But without emergency funding from Congress, "we may find ourselves halfway through a phase one trial and not being able to take that next immediate step" to phase two, he said.

Meanwhile, the threat of mosquitoes spreading the virus may increase with the rainy season in Puerto Rico and warmer weather in the continental U.S. Since mosquito control is usually the job of local government, Frieden said state and local officials have been invited to a day-long "Zika Action Summit" at CDC's Atlanta headquarters April 1st to help them prepare battle plans.